static bool TIFFInitLZW(TIFF tif, COMPRESSION scheme)
{
#if DEBUG
if(scheme!=COMPRESSION.LZW) throw new Exception("scheme!=COMPRESSION.LZW");
#endif
// Allocate state block so tag methods have storage to record values.
LZWCodecState sp=null;
try
{
tif.tif_data=sp=new LZWCodecState();
}
catch
{
TIFFErrorExt(tif.tif_clientdata, "TIFFInitLZW", "No space for LZW state block");
return false;
}
sp.dec_codetab=null;
sp.dec_decode=null;
sp.enc_hashtab=null;
sp.rw_mode=tif.tif_mode;
// Install codec methods.
tif.tif_setupdecode=LZWSetupDecode;
tif.tif_predecode=LZWPreDecode;
tif.tif_decoderow=LZWDecode;
tif.tif_decodestrip=LZWDecode;
tif.tif_decodetile=LZWDecode;
tif.tif_setupencode=LZWSetupEncode;
tif.tif_preencode=LZWPreEncode;
tif.tif_postencode=LZWPostEncode;
tif.tif_encoderow=LZWEncode;
tif.tif_encodestrip=LZWEncode;
tif.tif_encodetile=LZWEncode;
tif.tif_cleanup=LZWCleanup;
// Setup predictor setup.
TIFFPredictorInit(tif);
return true;
}
// LZW Decoder.
static bool LZWSetupDecode(TIFF tif)
{
LZWCodecState sp=tif.tif_data as LZWCodecState;
string module=" LZWSetupDecode";
if(sp==null)
{
// Allocate state block so tag methods have storage to record
// values.
try
{
tif.tif_data=sp=new LZWCodecState();
}
catch
{
TIFFErrorExt(tif.tif_clientdata, "LZWPreDecode", "No space for LZW state block");
return false;
}
sp.dec_codetab=null;
sp.dec_decode=null;
// Setup predictor setup.
TIFFPredictorInit(tif);
sp=tif.tif_data as LZWCodecState;
}
#if DEBUG
if(sp==null) throw new Exception("sp==null");
#endif
if(sp.dec_codetab==null)
{
try
{
sp.dec_codetab=new code_t[CSIZE];
for(int i=0; i<CSIZE; i++)
{
sp.dec_codetab[i]=new code_t();
sp.dec_codetab[i].next=-1;
}
}
catch
{
TIFFErrorExt(tif.tif_clientdata, module, "No space for LZW code table");
return false;
}
// Pre-load the table.
byte code=255;
do
{
sp.dec_codetab[code].value=code;
sp.dec_codetab[code].firstchar=code;
sp.dec_codetab[code].length=1;
sp.dec_codetab[code].next=-1;
} while((code--)!=0);
// Zero-out the unused entries
for(int i=CODE_CLEAR; i<CODE_FIRST; i++)
{
sp.dec_codetab[i].next=0;
sp.dec_codetab[i].length=0;
sp.dec_codetab[i].value=0;
sp.dec_codetab[i].firstchar=0;
}
}
return true;
}
// Reset encoding hash table.
static void cl_hash(LZWCodecState sp)
{
for(int i=0; i<HSIZE; i++) sp.enc_hashtab[i].hash=-1;
}
